1. Field of the Invention
The present invention relates to a ballast cleaning machine for cleaning a ballast bed supporting a track, which comprises a machine frame extending in a longitudinal direction and supported on the track by undercarriages for movement in an operating direction, two vertically and laterally adjustable endless ballast excavating chains sequentially arranged in the longitudinal direction for excavating ballast from the ballast bed and mounted on the machine frame between the undercarriages, drives for vertically and laterally adjusting, and for revolving, each endless ballast excavating chain, two track lifting devices mounted on the machine frame, a screening installation for cleaning ballast, a first conveyor arrangement for conveying the ballast excavated by the two endless ballast excavating chains to the screening installation, and a second conveyor arrangement for distributing the cleaned ballast from the screening installation to the ballast bed.
2. Description of the Prior Art
Ballast cleaning machines of this type have been disclosed in published German patent application No. 43 43 148 A1, French patent No. 1,029,167 and German Democratic Republic patent No. 240 043. These machines have a machine frame supported on undercarriages at the ends of the machine frame for movement on the track in an operating direction, and two excavating chains are mounted on the machine frame immediately following each other in the operating direction. A ballast cleaning screening installation is arranged between the two ballast excavating chains. While the machine continuously advances along the track, the first excavating chain, as seen in the operating direction, excavates the ballast and conveys it to the screening installation, and the second, trailing excavating chain removes the soil underlying the ballast bed. The removed soil is conveyed to trailing storage cars. Before the cleaned ballast is distributed from the screening installation, a protective sand layer is laid on the subgrade.
French patent No. 714,645 shows an arrangement of four endless bucket chains for raising excavated ballast and convey it to a screening installation.
Another machine for rehabilitating a ballast bed is disclosed in European patent application No. 0 629 744 B1. A first excavating chain excavates a layer of ballast, and the excavated ballast is comminuted in a stone crusher. The comminuted ballast is distributed on the excavated ballast bed and compacted to serve as a protective layer over the subgrade. A second excavating chain mounted on a second machine frame removes soil, which is replaced by the protective layer, whereupon the track is laid. In a subsequent operating stage, new ballast is introduced to provide a ballast bed.
It is the primary object of this invention to provide a ballast cleaning machine of the first-described type, which achieves a particularly high ballast cleaning efficiency with two endless ballast excavating chains which encompass the track.
The above and other objects are accomplished in accordance with the invention with a ballast cleaning machine for cleaning the ballast bed supporting a track, which comprises a machine frame extending in a longitudinal direction and supported on the track by undercarriages for movement in an operating direction, one of the undercarriages at an end of the machine frame being displaceable in the longitudinal direction. Two vertically and laterally adjustable endless ballast excavating chains are sequentially arranged in the longitudinal direction for excavating ballast from the ballast bed and mounted on the machine frame between the undercarriages, with drives for vertically and laterally adjusting, and for revolving, each endless ballast excavating chain. A respective operator""s cab is mounted on the machine frame in view of each endless ballast excavating chain, a control for the drives being arranged in each operator""s cab. Furthermore, at least two track lifting devices are mounted on the machine frame, a screening installation for cleaning ballast is mounted on a car linked to the machine frame, a first conveyor arrangement conveys the ballast excavated by the two endless ballast excavating chains to the screening installation, and a second conveyor arrangement distributes the cleaned ballast from the screening installation to the ballast bed.
A machine combining these features substantially enhances the ballast excavating capacity in a ballast cleaning operation so that very large screening installations may be used for cleaning the large volume of excavated ballast. By mounting two endless ballast excavating chains on a common machine frame, in connection with a correspondingly large excavating section obtained by the displaceable undercarriage, construction costs compared to the use of two machines are reduced despite the increase in operating efficiency.